Your HVAC system is made up of complex components, all of which serve very important functions in terms of heating and cooling your home. One of the most important components of your HVAC system is the thermostatic expansion valve (TXV). Like most of the other components, the thermostatic expansion valve is ideally designed to improve the efficiency of your HVAC system. In simple terms, it controls the flow of liquid refrigerant as it flows into the evaporator.

The thermostatic expansion valve basically does this at the same rate as the refrigerant being boiled inside the evaporator. It’s also important to note that it provides a much-needed pressure drop inside the HVAC system, hence separating the high-pressure side from the low-pressure one. By doing so, the thermostatic expansion valve facilitates more efficient heat transfer. The functions performed by the TXV are very important because they keep your HVAC system running. This is because if the liquid refrigerant for some reason is ever allowed to enter the compressor, your HVAC system would be severely damaged.

Read on to find out everything you need to know about the thermostatic expansion valve.

How Does the Thermostatic Expansion Valve (TXV) Work?

The thermostatic expansion valve is made up of a needle valve and a seat, adjusting screw, spring, and metallic diaphragm. As you might have learned by now, its main purpose is to ensure that the flow of the refrigerant load is regulated at all times.

The thermostatic expansion valve basically needs a capillary tube as well as a thermal element (bulb) to work properly. The main function of the capillary tube is to connect the bulb to the top of the TXV diaphragm.

In the event that the refrigerant load on the evaporator increases, it pushes the liquid refrigerant to boil faster than before inside the evaporator coil. Consequently, the temperature of the thermal element (bulb) will increase as a result of the evaporation of the liquid refrigerant. Therefore, the bulb’s pressure will increase, transmitting through the capillary tube to the diaphragm. This causes the diaphragm to move downwards and opens the thermostatic expansion valve for it to admit more refrigerant liquid to the evaporator. This process continues until pressure balance on the diaphragm is attained.

On the other hand, in the event that the refrigerant load on the evaporator decreases, it will mean that the amount of the refrigerant liquid that evaporates in the evaporator coil will also decrease. For this reason, the surplus refrigerant liquid will flow towards the evaporator outlet, hence cooling the bulb. As a result, the pressure inside the bulb decreases due to a decrease in its temperature. The low pressure inside the bulb is then transmitted through the capillary tube to the diaphragm, which in the end pushes the diaphragm in an upward direction.

This reduces the opening of the thermostatic expansion valve, thus reducing the flow of the refrigerant liquid to the evaporator. The pressure inside the evaporator reduces as the refrigerant liquid reduces. This process continues until the pressure inside the evaporator and the spring is in balance with the bulb’s pressure.

Functions of the Thermostatic Expansion Valve (TXV)

The TXV performs several functions inside the refrigerating system, which help the refrigerating system to work efficiently.

Controlling Action

One of the biggest functions of the TXV is that it helps with changing loads inside the refrigerating system. When the refrigerant load on the system increases, the thermostatic expansion valve opens up to let in more refrigerant liquid. On the other hand, when the refrigerant load decreases, the TXV operates in the opposite manner.

Modulating Action

Another important function of the thermostatic expansion valve is that it allows the right amount of refrigerant liquid inside the evaporator. Under no circumstance does the TXV flood or dry the evaporator with refrigerant liquid.

Throttling Action

The thermostatic expansion valve basically functions in the same way as any other valve you can think of. The TXV has a pressure drop across it which separates the high-pressure side from the low-pressure side of the HVAC system.

Applications of the Thermostatic Expansion Valve

Together with the capillary tube, the thermostatic expansion valve is used widely in most of the refrigeration and air conditioning systems in the market today. While the capillary tube is only used in small capacity systems such as domestic appliances, the TXV is used in commercial and industrial refrigerating and air conditioning systems of higher capacities.

The following are some of the common applications of the TXV:

  • Heat pump systems
  • Industrial refrigeration plants
  • Liquid chillers
  • Packaged air conditioners
  • High-capacity split air conditioners
  • Commercial units including icemaker machines, freezers, and supermarkets
  • Central air conditioners

Benefits of Thermostatic Expansion Valve

There are so many benefits associated with the thermostatic expansion valve. The thermostatic expansion valve ensures that the evaporator is fully active and helps in attaining the optimum cooling effect of the refrigerating system. In most cases, if the refrigerant entering the compressor has any liquid droplets, it compresses and could easily result in the breakdown of the compressor. However, the TXV ensures that the refrigerant in the evaporator is fully vaporized, which means that the chances of finding liquid particles inside the refrigerant are very low. This basically means that the TXV extends the life of the compressor.

The TXV primarily maintains a consistent flow of the refrigerant to the evaporator based on the refrigeration load inside. This means that the air conditioning or refrigeration plant can function according to the changing load requirements. The TXV also ensures that the compressor works at optimum capacity according to the refrigeration load on the refrigerating system. If the refrigerant load is less, the TXV is able to work on a lesser capacity to compress it, which means that the energy consumed will be minimal. On the other hand, if the refrigerant load is higher, the TXV works at a higher capacity.

Problems of the Thermostatic Expansion Valve

If superheating occurs inside the refrigerating system, the thermostatic expansion valve can never be used. Also, if the thermal element (bulb) is not in good contact with the refrigerating tube, the TXV won’t be able to work well. At times, the TXV is affected by moisture and contaminants, which causes it to jam or stick. This can easily lead to the TXV opening too wide or not open completely. Thus, it won’t be able to regulate the refrigerant properly.

Contact Us Today!

Are you looking for high-quality and reliable air conditioning services for your home? At Express Home Services, we have qualified and experienced technicians who are committed to delivering the best air conditioning, heating, indoor air quality, and electrical services you can find in the Las Vegas, NV, and Bountiful, UT, areas. We can take care of all of your thermostatic expansion valve concerns. Contact us today, and let us help you stay comfortable in your home throughout the year.

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